Release of POPs from Alpine glaciers

Mountainous regions such as the Alps represent a “cold trap” for atmospherically derived persistent organic pollutants (POPs) emitted in urbanized areas, due to the prevailing cold temperatures in combination with high precipitation rates. The awareness of the ubiquity of POPs such as dioxins, polychlorinated biphenyls (PCBs) and chlorinated pesticides in high-altitude regions and their conservation over long time periods leads to the hypothesis that melting Alpine glaciers may represent a secondary source of these “legacy pollutants”. Thus, POPs that were previously deposited to and incorporated into glaciers can now be released to the environment due to the rapid melting of glaciers.

Sediments of proglacial lakes, which form efficient traps of glacially-derived particles, provide ideal environmental archives of pollutants associated with particles. In annually layered sediment cores of proglacial Alpine lakes, we reconstruct time series of POPs, for which environmental contamination in Switzerland has significantly decreased during the last decades. Investigated lakes include Lej da la Tscheppa in the Upper Engadine, as well as Oberaarsee and Steinsee in the Bernese Oberland. As a high-altitude and non-glacial reference lake, Engstlensee in the Bernese Oberland is considered. These studies reveal a first peak of persistent chemicals in the 1960s-1970s, which can be attributed to their use and emissions at that time. Since the late 1990s input of pollutants into the glacier-fed lakes has sharply increased again, confirming the glacier hypothesis.

Currently we study the processes governing the transport of POPs through Alpine glaciers. We investigate the deposition on, the incorporation into, the transport within and the release from Alpine glaciers by a combination of chemical multimedia models and glacier models. First mass balance calculations reveal that the release of POPs from melting Alpine glaciers largely accounts for the observed increase of concentrations in sediment from proglacial lakes. These model calculations further support the glacier hypothesis. Moreover, we can track pollutant trajectories within Alpine glaciers and determine the temporal delay between initial deposition of pollutants in remote Alpine sites and their release from glaciers.

Contact Person: Flavio Anselmetti

Collaboration:
This interdisciplinary project is a close collaboration between different research teams covering complementary scientific fields. Involved groups include:

• Safety and Environmental Technology Group at ETH Zurich
  (Christian Bogdal, Martin Scheringer, Konrad Hungerbühler)
• Laboratory for Analytical Chemistry at Empa
  (Peter Schmid, Heinz Vonmont)
• Laboratory for Hydraulics, Hydrology and Glaciology at ETH Zurich
  (Martin Lüthi, Martin Funk)
• Analytical Chemistry research group, PSI
  (Margit Schwikowski)
  
  

Publications:
Bogdal, C.; Schmid, P.; Zennegg, M.; Anselmetti, F. S.; Scheringer, M.; Hungerbühler, K., 2009, Blast from the past: Melting glaciers as a relevant source for persistent organic pollutants: Environ. Sci. Technol. 43, 8173–8177. (pdf, 6.42MB)

Bogdal, C.; Schmid, P.; Zennegg, M.; Anselmetti, F. S.; Scheringer, M.; Hungerbühler, K., 2009, History repeats itself: Persistent organic pollutants in the glacier-fed Lake Oberaar, Switzerland. Organohalogen Compounds.

Bogdal, C.; Schmid, P.; Zennegg, M.; Sturm, M.; Scheringer, M.; Hungerbühler, K., 2009, The haunting legacy: Sediment record of persistent organic pollutants in the glacier-fed Lake Tscheppa, Switzerland. Organohalogen Compounds.

Blüthgen N., 2009, Reconstruction of historical inputs of persistent organic pollutants (POPs) in remote Alpine lakes in Switzerland. Master Thesis, University of Zurich.